This invention relates to sliders for adjustment of the suspension of a wheeled vehicle longitudinally with respect to a trailer body of the vehicle, and more particularly, to a system for facilitating such adjustment.
Frequently, tandem axle trailers and like vehicles cannot always be loaded equally throughout their length with the result that the loads bearing on the wheels supporting the vehicle are not always uniform. Many prior devices have been devised to compensate for this unbalanced load condition. Typically, the device for compensating an unbalanced load must be adjustable while the vehicle is loaded, for it is only at this time that the operator of the vehicle can determine the correct position for equally distributing the load. Since the variation of position must be accomplished when the vehicle is loaded, the means connecting the sub-frame to the vehicle must be adapted to allow such adjustment in a relatively easy manner while under the influence of a substantial load. Conventional slider devices used for this purpose typically comprise a pair of side rails secured at the left and right sides of the vehicle trailer in a fixed position extending longitudinally of the trailer, and a sub-frame which carries the suspension comprising left and right slide members slidable of the trailer on the side rails, Typically, a plurality of locking pins lock the sub-frame in various positions of adjustment relative to the side rails. The locking pins are retractable, permitting adjustment of the sub-frame to selected positions of adjustment and may be extendable for locking the sub-frame in a select position of adjustment. A linkage is provided for moving the locking pins from the extended position to a retracted position and from the retracted position to the extended position. Typically, the linkage is operable to retract the pins by moving a pull rod which extends laterally outwardly from the side of the sub-frame.
The pull rod and linkage design described above has been used for many years, but has a serious drawback. The locking pins often become stuck in the extended position due to the pins being wedged in openings in the slider sub-frame, thus making it difficult if not impossible to operate the pull rod to retract the pins to facilitate the adjustment. When one or more pins become stuck, the operator of the vehicle must jostle the trailer by driving the vehicle forwardly or rearwardly in short increments until the pins are sufficiently free to enable the pull rod to be operated. Such a procedure is inconvenient and time consuming particularly if there is only one person operating the vehicle, since while jostling the trailer to free the pins, there is no indication to the vehicle driver when the pins are freed. Thus, upon jostling the trailer, the operator must move from the cab of the vehicle to the location of the pull rod to determine whether the pins are freed and if the pins are not freed, must return to the cab and repeat the jostling procedure. Such procedure is not as troublesome when there is a second person available, since the second person may pull on the pull rod while the trailer is being jostled to free the pins and then so indicate to the person jostling the vehicle. However, a second person is not always available.
A slider system has been disclosed which attempts to solve this problem. U.S. Pat. No. 4,838,578 discloses a slider having a mechanism for retracting locking pins biased by associated pin springs. The mechanism comprises a linkage interconnecting the locking pins for conjoint movement of the pins between extended and retracted positions. A manually movable handle actuates the linkage. A handle spring is associated with the handle and is configured to be strong enough to overcome the force of the pin springs. The handle spring will deflect when one or more pins are in a stuck condition which permits the handle to move outwardly while maintaining a force urging rotation of a crank of the linkage to effect articulation of the pins. The handle can be locked in its outward position and the vehicle can be jostled to free the pins. Once the pins are freed, the force of the deflected handle spring causes the crank to rotate to retract the pins. However, when one or more pins are stuck, a significant manual effort is required by the operator to move the handle to a position whereby the handle spring deflects so as to assist in moving a stuck pin to an unstuck condition.
Accordingly, a need exists to provide a slider locking system for retracting and extending locking pins of a slider sub-frame to permit adjustment of a suspension of a vehicle longitudinally of the body of the vehicle which may be operated with minimal effort by one person, even in the event the locking pins become stuck during retraction thereof.